I can only answer with what I'd be shopping for under ficticious circumstances. The pack I bought on sale (because discontinued) in early 2006 is holding up just fine, which is why my scenario is fictitious. I suspect my current pack (from Six Moon Designs) will outlast me!
My need for a pack is one that will easily support 25 lbs. and about 45 liters volume by transferring 95% of the weight to the hip belt and with load lifters that will allow me to keep the tops of the shoulder straps away from my pressure-sensitive shoulders. The pack needs to fit close to my back so I'm not pulled off balance. I also don't want a pack that has a lot of gewgaws (although I do want outside pockets to hold water, snacks, rain gear and a wet tent). My pet peeve is hip belt pockets because the item I want is never in the first pocket I open! I also want a pack that weighs no more than 2 lbs. Unlike you, I don't care at all about style, just comfort.
If I were looking for a replacement pack, I'd start with the ULA Ohm 2.0 or Circuit (although the latter is slightly over my max desired weight) or the Elemental Horizons Kalais. Since our criteria are far apart, those may not interest you at all, but it might be worth your while to take a look at them (and other packs by the same manufacturers) online. Other "cottage industry" packs that might be worth a look are those made by Six Moon Designs or Gossamer Gear, and ZPacks. Mountain Laurel Designs is good but their frameless packs mean your total pack weight shouldn't exceed 20 lbs.
What you really neeed before shopping for a pack are the following parameters: (1) Weight to be carried, including weight of the pack (be sure it's several pounds--preferabl;y 5--below the maximum suggested weight for the pack on the manufacturer's website); (2) volume of gear to be carried; (3) your torso length (from the knob at the base of your neck to a point on your spine halfway between your two iliac crests (not your waist). There's a slightly titillating video on the ULA website that shows how to measure, but get someone to measure for you (i"ve come out as much as 3" difference each time when trying to measure myself).
Also, have your gear (including the weight/volume equivalent of a week's food and a day's water) ready to load up in the pack as soon as it arrives. Leave the tags on, keep the pack clean, load it up and hike around the house for a few hours to judge the comfort. If it's not, return it! You may have to pay return shipping for several packs before you find the one that is perfect for you.
If going to a store (where I never had much luck, but each of us is different), pack up the aforesaid gear and dummy food/water and take it to the store with you. The store staff will be appreciative (and therefore more helpful) if you make an appointment in advance during less crowded hours.
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey